The Angels didn't "offer" him anything. They're legally on the hook to pay this scumbag. They managed to sucker someone else into picking up (a relatively small) part of the check, and got him to go away at the same time, is all.
The reality is, in the end, if the Angels fought it, they'd extend the drama out for months, perhaps a year or two, pay exorbitant fees to their lawyers, and probably in the end still have to pay at least something to Hamilcaine. Instead they got the equivalent of being paid $15 million not to go to court.